Base emitter voltage and collector current

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Discussion Overview

The discussion revolves around the relationship between base-emitter voltage (VBE) and collector current in a transistor. Participants explore how changes in VBE affect base current and subsequently collector current, addressing both theoretical and practical implications.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions whether a decrease in base-emitter voltage leads to a decrease in collector current, suggesting that a lower VBE might increase base current and thus collector current.
  • Another participant asserts that a decrease in VBE actually decreases base current, referencing the characteristics of a p-n junction diode.
  • A participant emphasizes that VBE acts as a barrier voltage, arguing that a decrease should logically increase base current.
  • Further discussion includes a formula for base current, indicating that an increase in VBE results in a decrease in base current, which could imply a decrease in collector current.
  • Another participant introduces a formula for current through a junction, suggesting that understanding the junction characteristics is crucial before considering external components.
  • It is noted that base current and collector current are related through the transistor's Beta, which is dependent on collector current.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between base-emitter voltage and collector current, with no consensus reached on the implications of decreasing VBE.

Contextual Notes

Participants reference various equations and characteristics of p-n junctions, indicating that the discussion involves complex interactions between voltage, current, and external circuit elements. Some assumptions about the circuit configuration and parameters are not fully explored.

ranju
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Does decrease in value of base-emitter voltage decreases collector current..??
As I studied that decrease in base-emitter voltage of some part of signal to lesser ammplification of that part due to smaller current..but how base emitter voltage is leading to less collector current..
because if base-emitter voltage decrease , base current increase which further increase collector current..
 
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ranju said:
Does decrease in value of base-emitter voltage decreases collector current..??
Yes.

As I studied that decrease in base-emitter voltage of some part of signal to lesser ammplification of that part due to smaller current..but how base emitter voltage is leading to less collector current..
because if base-emitter voltage decrease , base current increase which further increase collector current..
If VBE decreases, base current decreases. It's a p-n junction, so the characteristic is that of a p-n junction diode. If the forward voltage increases, the forward current increases.
 
But base-emitter voltage is a barrier voltage.. so if it decreases , base current should increase..!
 
ranju said:
But base-emitter voltage is a barrier voltage.. so if it decreases , base current should increase..!
No. NascentOxygen has given you the correct answer. Consider the Base-Emitter Voltage curves:

basemit.gif


Check out these Base-Emitter Junction Details.
 
But is'nt there any logic behind it...??
because if we see this equ.
Ib=Vb/Rb - Vbe/Rb
so from this equ. it can be seen that if Vbe increase base current decrease..!
 
have you ever run across the formula for current through a junction,
I=eqv/kt
where v would be your Vbe ?
That's what dlgoff's graph is showing you.


because if we see this equ.
Ib=Vb/Rb - Vbe/Rb
so from this equ. it can be seen that if Vbe increase base current decrease..!

that involves not only Vbe but an external Vb and an external Rb.

Your original question
Does decrease in value of base-emitter voltage decreases collector current..??
did not involve either.

It is important to be rigorous in your thinking. Focus on the junction, after you've figured it out then add the external components.

Base current and collector current are related by the transistor's Beta,
which itself is a function of collector current...
 

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